This is a double-blind, placebo-controlled, crossover study of 20 women with menstrual migraine or menstrually-related migraine attacks. The objectives of this trial are to evaluate the efficacy of 6 mg of sumatriptan, administered subcutaneously, in treating menstrual migraine, and to enhance understanding of the underlying pathophysiology of menstrual migraine by monitoring plasma 5-HIAA, the serotonin metabolite. Each subject will be treated for a migraine associated with 2 separate menstrual cycles, receiving sumatriptan or placebo in random order.